The number of nebulae increased dramatically thanks to the efforts of William Herschel and his sister Caroline Herschel. Their Millennium Catalog entitled New Nebulae and Star Clusters was published in 1786. The second thousand year catalog was published in 1789 and the third catalog with number 510 Sahabhi was published in 1802. During his research, William Herschel believed that these nebulae are actually unresolved star clusters. However, in 1790 he discovered a star surrounded by a nebula and concluded that the discovered dust structure was real, not just a distant star.
William Huggins In 1864, he studied the spectra of 70 nebulae. He found that a third of the nebulae have the emission spectrum of a gas. The rest showed continuous spectra and were thought to be composed of stellar mass. The third category was published in 1912 by Westo Silver.
In 1923, after much debate, it became clear that many nebulae were actually galaxies further away than the Milky Way. Silver and Hubble continued to collect spectra of various nebulae and discovered 29 nebulae with emission spectra and 33 nebulae with starlight spectra.
There are countless beautiful and well-known nebulae in the world. In this section, we introduce a short list of famous nebulae that have been the subjects of huge telescopes such as the Hubble Space Telescope and James Webb.